They were under investigation by the police for much of the time that they were there. 

If he takes care of your place and does not get social visits from the police, then just keep getting the late fee or any extra "inconvenience fee" you deem fit on the lease renewal in the form of a rent increase.

The person viewing the apartment said “is there a police officer that lives here”?

There is a board of supervisors that make decisions on the township (or borough, etc) in regards to ordinances, road maintenance, police force, oversee the budget for income from property taxes.  

We got the police involved and told them what happened, but she refused to file a report because she didn't want to get him in trouble or put him in jail.Well, he was able to do that all on his own.

A police officer has no training to even know if a lease is valid at all.

You also need duck feathers and an umbrella; you need to let things like overdoses, police visits, prostitution, underage drinking, breakage, theft, accidents, lawsuits and other common things like that slide off your back. 

Condo Association complained to me and to  local police about this  situation as unit as  has foul smell and bugs all over .Local Police went inside the property and found that no one is living there and place is full trash and clothes all over the place .I have started the  eviction process but that will take another month before i can get possession of my property.

Police and LT are not looking to help.

Saying/doing nothing and blaming yourself or your lack of DD is no better than a street full of neighbors who see an innocent person gunned-down but are silent to the police.